Today, we cross Wallace's line. The University of Houston's
College of Engineering presents this series about the machines that
make our civilization run, and the people whose ingenuity created
them.

Physiologist Jared Diamond makes a pilgrimage to Wallace's
line -- an imaginary line separating Borneo and Java from the
Celebes and other islands to the southeast. "[Crossing] that line,"
he says, "may have been what made our ancestors truly human."

Alfred Russel Wallace was the now-almost-forgotten
co-discoverer of the theory of evolution. Darwin had pretty well
formulated the theory when he learned that Wallace was about to
publish a similar idea. When Wallace heard about Darwin, he
politely stood aside and let Darwin publish first.

Among many contributions, Wallace identified the demarcation
between species of southeast Asia and completely different species
in Australia and New Guinea. There are other such regions. The
Sahara is one. A band from northwest India through the Himalayas
and Indochina forms another such zone of separation. But
Wallace's line has special importance.

For a long time, we've known that modern humans evolved in
Africa 100,000 or so years ago, and that they began making dramatic
art and tools in Europe 30 or 40 thousand years ago. But we've
paid scant attention to the world southeast of Wallace's line.

The so-called Java Ape Man fossils make it clear that
ancestors of modern humans reached southeast Asia a million years
ago. Java Man got as far as Borneo and Java over land links that
existed before the glacial epochs. But those links ended there,
and he couldn't get to New Guinea and Australia.

Yet modern humans have occupied Australia for 60,000 years.
Somehow, modern humans appeared in Java Man's world, and they
managed to go island-hopping all the way to Australia. There they
practiced advanced art and technology that rivals what we find in
the caves of central Europe. The catch is, they did so
much earlier than the European Cro-Magnons.

And so, Jared Diamond observes, we were the one species that
lived on both sides of Wallace's line. The crucible of human
creativity might well have been Australia. He believes the art and
technology of Australian aborigines slowly trickled back and
eventually reached Europe. Diamond thinks that crossing Wallace's
line was the giant step that made us into a technological species.

Eventually, the vast geography and resources of Eurasia allowed
the aborigines' cousins to run ahead -- to invent writing and the
wheel, to build canons and cathedrals. Eventually, when Dutch and
English navigators found their way back to Australia, all they saw
were shockingly primitive humans. They had no way to see the
sophistication of their survival strategies.

And they had no idea they should be saying "Thank you" to
their ancient teachers.

I'm John Lienhard, at the University of Houston, where
we're interested in the way inventive minds work.